Dynamic geometry of the left ventricular outflow tract of pigs with induced supravalvular aortic stenosis.

OBJECTIVES Detailed information about the dynamic geometry of the left ventricular outflow tract (LVOT) is of great importance for transcatheter aortic valve implantation (TAVI), since these valves utilize the LVOT as a landing zone for optimum placement and fixation. The LVOT is generally considered circular in shape and stable in its conformation. However, recent studies indicate that this may not be the case. METHODS Twenty-two 5-kg pigs (± 0.47 kg) were randomly allocated to either aortic banding (n = 14) or sham operation (n = 8). LVOT dynamic geometry was assessed using cardiovascular-magnetic resonance imaging, 9 weeks after banding of the ascending aorta. RESULTS All the banded animals developed significant left ventricular hypertrophy (P = 0.01) compared with controls. All the animals demonstrated significant reduction in eccentricity index (P(intervention) < 0.01, P(control) < 0.05) and longest internal diameter (P(intervention) < 0.01, P(control) = 0.02) when comparing measurements from end-diastole to end-systole. No significant systolic or diastolic differences were found between the two groups. CONCLUSIONS The main findings were: the LVOT (i) undergoes substantial geometric alterations throughout the cardiac cycle and (ii) is ellipsoid throughout the cardiac cycle, (iii) geometric changes during the cardiac cycle stems from compression of the long-axis of the LVOT and (iv) dynamic geometry did not change significantly after induction of significant LV hypertrophy. Thus, our data suggest that assumptions made in daily practice, of a circular and stable LVOT geometry, need to be revised.